Bit assembly for down-hole drills

ABSTRACT

A bit assembly is for a drill having a casing, a central axis and a hammer movably disposed within the casing. The bit assembly includes a chuck with a tubular body having first and second ends, the first end being connected with the casing such that the second end is spaced axially therefrom, and one or more openings extending generally axially from the second end toward the first end. A bit includes a body with a tubular portion having a cavity and one or more axial lugs, the lug(s) being disposable within the chuck opening(s). A retainer is coupled with the chuck, disposable within the bit cavity and engageable with the bit lug(s) so as to releasably couple the bit with the chuck. The retainer is preferably a deflectable ring sized to receive a portion of the hammer, such that the hammer prevents disengagement of the retainer from the bit.

The present invention relates to a down-hole drills, and moreparticularly to bit assemblies for reverse circulation down-hole drills.

Down-Hole drills are typically fluid-operated and generally include acasing, a hammer movably disposed within the casing, and a cutting bitwith a cutting surface movably coupled with the casing. The hammer islinearly reciprocated within the casing to repeatedly impact the bit soas the drive the cutting surface into a work surface of a hole beingdrilled. Typically, such drills further include a chuck for guiding themovement of the bit and/or the hammer. Often, the bit is movablydisposed within a chuck central bore and the bit and chuck havecomplementary grooves and splines that slidably interact during movementof the bit. Further, the bit is generally secured to the casing by meansof a set of split rings that engage with the outer surface of the bit,such as with a bit groove or shoulder, so as to connect the bit with thecasing.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a bit assembly for a drill, thedrill including a casing and a hammer movably disposed within the casingand having an end. The bit assembly comprises a bit having a cavity anda retainer connected with the casing. The retainer is disposable withinthe bit cavity and releasably engageable with bit so as to couple thebit with the casing.

In another aspect, the present invention is also a bit assembly for adrill, the drill having a casing and an axis extending centrally throughthe casing. The bit assembly comprises a chuck including a generallytubular body with first and second ends, the first end being connectedwith the casing such that the second end is spaced axially from thecasing, and at least one opening extending generally axially from thesecond end toward the first end. A bit includes a body with a tubularportion, the tubular portion having a cavity and at least one axial lug,the lug being at least partially disposable within the chuck opening.Further, a retainer is coupled with the chuck, disposable within the bitcavity and engageable with the at least one bit lug so as to releasablycouple the bit with the chuck.

In a further aspect, the present invention is again a bit assembly for adrill, the drill having a casing. The bit assembly comprises a chuckincluding a generally tubular body with a first end connected with thecasing, an opposing second end, a central axis extending between the twoends, inner and outer circumferential surfaces, and at least two throughslots each extending generally axially from the second end toward thefirst end and generally radially between the inner and outer surfaces. Abit includes a body with a central axis, the body having a generallycylindrical portion with a cutting surface and at least twocantilever-like lugs extending generally axially from the base portionand spaced circumferentially about the axis. Each lug is disposablewithin a separate one of the chuck through slots, the bit being movablycoupled with the chuck such that the lugs displace generally axiallywithin the chuck holes as the bit moves axially with respect to thechuck.

In yet another aspect, the present invention is once again a bitassembly for a drill, the drill having a casing. The bit assemblycomprises a chuck connected with the casing and having a generallytubular body, the tubular body having first and second ends, a centralaxis extending between the two ends, and at least one of an openingextending generally axially from the second end toward the first end anda generally axial lug. A bit has a body with a generally tubularportion, the tubular body portion having a first end connected with aremainder of the body and a second end, and a cavity extending inwardlyfrom the second end. The bit has at least one of an opening extendinggenerally axially from the second end generally toward the first end andconfigured to receive at least a portion of a chuck lug and a generallyaxial lug disposable within a chuck opening. Further, a retainer iscoupled with the chuck, disposable within the bit cavity and engageablewith the bit tubular portion so as to releasably connect the bit withthe chuck.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the detailed description of thepreferred embodiments of the present invention, will be betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the invention, there is shown in the drawings,which are diagrammatic, embodiments that are presently preferred. Itshould be understood, however, that the present invention is not limitedto the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 is an axial cross-sectional view of a down-hole drill including abit assembly in accordance with the present invention;

FIG. 2 is an enlarged, partly broken-away view of a lower end of thedrill of FIG. 1;

FIG. 3 is another view of the drill lower end of FIG. 2, shown with acasing being displaced from a bit at the beginning of drill extractionoperation;

FIG. 4 is partly broken-away, perspective view of a lower portion of thedrill and bit assembly, shown with a chuck of the bit assembly in axialcross-section and a bit and retainer of the bit assembly in perspective;

FIG. 5 is an enlarged, partly away, broken-away perspective view of thedrill lower end, shown with the chuck and bit in axial cross-section andthe retainer in perspective;

FIG. 6 is a perspective view of the bit assembly;

FIG. 7 is another perspective view of the bit assembly, shown with thebit separate from the chuck and retainer;

FIG. 8 is a top plan view of the retainer;

FIG. 9 is an axial cross-sectional view of the retainer through line 9-9of FIG. 8;

FIG. 10 is an axial cross-section of the chuck;

FIG. 11 is a bottom plan view of the chuck;

FIG. 12 is an axial cross-sectional view of the bit;

FIG. 13 is a top plan view of the bit;

FIG. 14 is an axial cross-sectional view of the bit assembly, shownaligning the bit for connection with the chuck;

FIG. 15 is an axial cross-sectional view of the bit being connected withthe chuck, showing an upward force applied to the bit to cause the bitlug shoulders forcing the retainer to an inner radial position;

FIG. 16 is an axial cross-sectional view of the bit assembly, showingthe bit lugs shoulders displacing axially upwardly against the retainer;

FIG. 17 is an enlarged view of the retainer and bit lug shoulders ofFIG. 16;

FIG. 18 is an axial cross-sectional view of the bit assembly, showingthe bit lugs engaged with the retainer to releasably couple the bit withthe chuck;

FIG. 19 is a radial cross-section view of the bit assembly though line19-19 of FIG. 18;

FIG. 20 is an enlarged view of the retainer and bit lug shoulders ofFIG. 18;

FIGS. 21A-21C, collectively FIG. 21, are each an axial cross-sectionalview of the bit assembly, showing the coupled bit at respectively alower limit axial position, an intermediate axial position, an upperlimit axial position; and

FIG. 22 is an axial cross-sectional view of the lower end of the drill,showing a pusher tool displacing a hammer of the drill to enable removalof the bit.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, left”, “lower”, “upper”,“upward”, “down” and “downward” designate directions in the drawings towhich reference is made. The words “inner”, “inwardly” and “outer”,“outwardly” refer to directions toward and away from, respectively, adesignated centerline or a geometric center of an element beingdescribed, the particular meaning being readily apparent from thecontext of the description. Further, as used herein, the word“connected” is intended to include direct connections between twomembers without any other members interposed therebetween and indirectconnections between members in which one or more other members areinterposed therebetween. The terminology includes the words specificallymentioned above, derivatives thereof, and words of similar import.Furthermore, the term “position” is used herein to indicate a position,location, configuration, orientation, etc., of one or more components ofthe bit assembly and each is depicted in the drawings with reference toa randomly selected point on the item being described. Such points inthe drawing figures are randomly selected for convenience only and haveno particular relevance to the present invention.

Referring now to the drawings in detail, wherein like numbers are usedto indicate like elements throughout, there is shown in FIGS. 1-22 a bitassembly 10 for a down-hole, percussive drill 1 including a casing 2 anda hammer 3. The casing 2 has opposing ends 2 a, 2 b, an interior chamber2 c, and an axis 2 d extending centrally between the ends 2 a, 2 b. Thehammer 3 is movably disposed at least partially within the casingchamber 2 c so as to reciprocally displace linearly along the axis 2 d,and has a working or “strike” end 3 a. The bit assembly 10 basicallycomprises a chuck 12 connected (or connectable) with the casing 2, a bit14 having a cutting surface 15 and a cavity C_(B) configured to receivethe hammer end 3 a, and a retainer 16 disposable within the bit cavityC_(B) and configured to movably and releasably couple the bit 14 withthe chuck 12. Preferably, the bit assembly 10 also includes a skirt 13connected with the casing 2 and configured to enclose at least portionsof the chuck 12 and the bit 14, as described below.

The chuck 12 is configured to movably connect the bit 14 with the casing2; that is, the retainer 16 is connected with the chuck 12 and isengageable with the bit 14 to movably couple or retain the bit 14with/to the chuck 12, and thus also with the casing 2. Preferably, thechuck 12 has a cavity C_(C) and the retainer 16 is simultaneouslydisposable within the chuck cavity C_(C) and the bit cavity C_(B), thetwo cavities C_(C), C_(B) being at least partially overlapping orcoincident when the two components 12, 14 are movably coupled. Further,the bit 14 also has an interior contact or “impact” surface 17 boundingan inner axial end of the bit cavity C_(B) and is axially displaceablewith respect to the chuck 12 and the casing 2. Specifically, the bit 14is movable between a first, upper limit position A₁ (FIGS. 2, 5, 21C)and a second, lower limit position A₂ (FIG. 3, 18, 21A), whether suchmovement is due to displacement of the bit 14 or of the chuck 12 (i.e.,and casing 2). The hammer strike end 3 a is slidably disposable withinthe retainer 16 and within both the chuck and bit cavities C_(C), C_(B)so as to impact or strikingly engage the bit impact surface 17,displacing the bit 14 toward the lower limit position A₂ and/or drivingthe cutting surface 15 into a work surface S_(W) (FIG. 2) as discussedin further detail below.

Preferably, the chuck 12 includes at least one and preferably aplurality of clearance openings 20 and the bit 14 includes at least oneand preferably a plurality of axial lugs 22 each disposable within aseparate one of the chuck clearance openings 20. As the bit 14 movesrelative to the chuck 12, the bit lugs 22 linearly displace (i.e.,axially) through the chuck openings 20. As such, the chuck 12 and bit 14are essentially “telescoping” but without radial overlapping of the twocomponents 12, 14, i.e., the engaged portions of the chuck 12 and bit 14have at least generally the same outside diameter OD_(C), OD_(B), asdiscussed below. Further, when the retainer 16 is disposed withincoincident sections of the bit cavity C_(B) and the chuck cavity C_(C),the retainer 16 is simultaneously connected with the chuck 12 andengageable with or by one or more bit lugs 22 to releasably (andmovably) connect the bit 14 and the chuck 12, as discussed in greaterdetail below.

Further, the retainer 16 preferably includes a generally radial catchsurface 19 facing generally axially upwardly toward the casing 2, whichis contactable by a generally axially downwardly facing stop surface 23of each bit lug 22 when the bit 14 is located at the lower limitposition A₂. As such, contact between the retainer catch surface 23 andbit stop surface 23 prevent axial displacement of the bit 14 beyond thebit lower limit position A₂ (FIGS. 3, 18, 21) (i.e., in a first,downward axial direction d₁), thus preventing inadvertent removal of thebit 14 from the chuck 12. Further, the lugs 22 also contact the chuck 12at the upper limit position A₁, so as to thereby prevent furtherdisplacement in a second direction d₂ toward the casing 2. As such, theupper end of each bit lug 22 is thereby movably retained between theretainer 16 and the upper, closed ends of the chuck clearance openings20, as discussed in greater detail below.

Referring now to FIGS. 3, 8, 9, and 16-19, the retainer 16 preferablyincludes a generally annular body 24 having a central bore opening orbore 26 configured to receive the hammer end 3 a, such that the hammer 3is slidably displaceable through the retainer body 24. When the hammerend 3 a is disposed within the retainer bore 26, the hammer 3 preventsdisengagement of the retainer 16 from the bit 14. Specifically, theretainer 16 is preferably configured to be at least partially radiallydisplaceable between an outer radial position R_(O) (see, e.g., FIGS. 20and 21) and an inner radial position R_(I) (FIGS. 16 and 17) and mostpreferably collapsible or radially deflectable between the two positionsR_(O), R_(I), as discussed below. At the outer position R_(O), at leasta portion of the retainer 16 is releasably engaged with the bit 14 so asto thereby connect the bit 14 with the casing 2 (see, e.g., FIG. 20). Asbest shown in FIG. 17, at the inner radial position R_(I), the retainer16 is generally disengaged from, or nonengageable with, the bit 14 suchthat the bit 14 is disconnectable from the casing 2. More specifically,the retainer body 24 has an outer diameter that varies between maximumvalue OD_(max) (FIG. 20) at the outer position R_(O), at which theretainer 16 is engageable with/by the bit 14 (i.e., contactable by thestop surface 23) and a minimum value OD_(min) (FIG. 17), at which thebit 14 is axially displaceable about the retainer 16, as described ingreater detail below.

Referring to FIGS. 2, 3, 17 and 20, with such a retainer structure, thehammer 3 prevents displacement of the retainer 16 to the inner positionR_(O) when the hammer end 3 a is disposed within the retainer bore 26,thereby retaining the bit 14 connected with the chuck 12, as discussedin further detail below. More specifically, the retainer bore 26 has aninner diameter that varies between maximum and minimum values ID_(max)(FIG. 20) and ID_(min) (FIG. 17), respectively, as the retainer body 24radially displaces or deflects between the inner and outer positionsR_(O), R_(I). The hammer 3 has an outer diameter OD_(P) (FIG. 3) with aconstant value that is greater than the retainer inner diameter minimumvalue ID_(min) (but at least slightly lesser than the maximum valueID_(max)), such that retainer 16 cannot displace to the inner positionR_(I) when the hammer 3 is disposed within the bore 26, as best shown inFIG. 3.

Referring particularly to FIGS. 8 and 9, the retainer body 24 ispreferably formed as a generally circular ring 25 with ends 25 a, 25 bspaced by an axial gap 27, generally similar to a “snap ring”. As such,the retainer 16 generally radially displaces or deflects between theinner and outer positions R_(I), R_(O) by moving the ends 25 a, 25 b togenerally open and close the gap 27. That is, as the ring gap 27 isclosed, the retainer ring 25 collapses or deflects inwardly toward thebody inner position R_(I), and vice-versa. Further, the ring 25preferably has generally “frustatriangular” axial cross-sections CSR(FIG. 9), such that the body 24 has first and second angled, outercircumferential surfaces sections 29A, 29B, and a central outercircumferential surface 29C extending axially between the two angledsurfaces 29A, 29B. The first angled surface 29A provides at least aportion of the retainer catch surface 19, as discussed above, and eachangled surface 29A, 29B also functions as a driven surface engageable bythe bit lugs 22 to displace the retainer between the outer and innerpositions R_(O), R_(I), as described below.

Although a one-piece annular ring 25 is presently preferred, theretainer body 24 may alternatively be formed in any other appropriatemanner that enables the retainer 16 to function generally as describedherein. For example, the retainer body 24 may include two or morearcuate segments (not shown) defining a bore for receiving the hammer 3,being separately (but generally simultaneously) displaceable radiallybetween inner and outer positions, and configured to retain the bit 14coupled with the chuck 12 when located at the outer positions. The scopeof the present invention encompasses these structures described orsuggested herein, and all other appropriate structures that enable thebit assembly 10 to function generally as described herein.

Referring to FIGS. 6, 7, 10, 11, and 14-20, the chuck 12 preferablyincludes a generally tubular body 28 with first and second ends 28 a, 28b and a central axis 30 extending between the two ends 28A, 28 b. Thebody first end 28 a is connectable with the casing 2, and preferably hasexterior threads 32 engageable with corresponding interior threads (notindicated) of the casing 2, thus releasably connecting the chuck 12therewith. When the chuck body 28 is connected with the casing 2, thechuck axis 30 extends generally collinearly with the casing axis 2 d andthe body second end 28 b is spaced axially from the casing lower end 2b. The chuck body 28 has a central bore 31 providing the chuck cavityC_(C) and being sized to receive the hammer 3 such that the hammer 3 isslidably displaceable therethrough. Preferably, the chuck bore 31includes a guide surface section 33 having a inner diameter ID_(GS)(FIG. 10) that is slightly greater than the hammer outside diameterOD_(H), which acts to center the hammer 3 on the casing axis 2 d as thehammer reciprocates during a drilling operation. The guide surface 31also functions to assist in the timing of the exhaust flow through thehammer 3, as hammer exhaust ports 3 b (see FIG. 4) are sealed whendisposed within the cylinder guide surface 31. Thus, the chuck surface31 alternatively opens and closes the exhaust ports 3 b depending on theposition of the hammer 3 with respect to the chuck 12.

Further, the chuck body 28 has at least one and preferably a pluralityof circumferentially spaced, elongated slotted through holes 34extending generally axially and inwardly from the body second end 28 btoward the body first end 28 a, each slotted hole 34 providing one chuckclearance opening 20, as described above. Most preferably, the chuckslotted through holes 34 are sized and spaced so as to define aplurality of chuck lugs 36, i.e., between adjacent pairs of holes 34,which are disposable within corresponding bit openings 48, as discussedbelow. Specifically, each chuck lug 36 extends axially from a generallyenclosed sidewall portion 38 of the tubular body 28 (i.e., the remainderof the body 28 not “cut through” by the holes 34) to the body second end28 b. Further, each clearance hole 34 has a radial open end 34 a and ispartially bounded by a generally arcuate, axial surface providing one ofthe above-described stop surfaces 35. Specifically, each stop surface 35is engageable/contactable with one of the chuck lugs 22 to generallyprevent axial movement of the bit 14 in the second direction d₂ beyondthe bit upper position A₁, as described above and in additional detailbelow.

Preferably, each chuck lug 36 includes a generally rectangular,cantilever-like body 37 having a first end 37 a connected, andpreferably integrally formed with, the chuck enclosed sidewall portion38, and a second, free end 37 b spaced axially from the first end 37 a.Each lug body 37 has inner and outer, generally circumferential surfaces37 c, 37 d, the outer surfaces 37 d of all the chuck lugs 36collectively defining the chuck outside diameter OD_(C), as discussedabove and in further detail below. Also, each lug body 37 further hasopposing radial contact surfaces 41 extending axially between the bodyfirst and second ends 37 a, 37 b and slidable against correspondingsurfaces of the bit lugs 20, as described in below. Preferably, each lugbody 37 further includes an inner circumferential groove 39 extendingradially outwardly from the lug inner surface 37 d, each groove 39 beingconfigured to receive a portion of the retainer annular body 24.

Specifically, each lug groove 39 has generally triangular axialcross-sections, a width w_(g) (FIG. 10) that is generally equal to theaxial thickness t_(a) (FIG. 9) of the retainer annular body 24, and adepth d_(g) such that the plurality of grooves 39 collectively define aninside diameter (not indicated) that is at least slightly lesser thanthe maximum outside diameter OD_(MAX) of the retainer annular body 26.As such, the retainer body 24 is simultaneously disposable within all ofthe chuck lug grooves 39 so that the retainer 16 is frictionallyconnected with the chuck 12. That is, the preferred ring body 25 isinwardly collapsed or deflected so as to fit inside the chuck cavityC_(B) and is then positioned axially adjacent to the chuck grooves 39.Thereafter, the ring 25 is allowed to deflect outwardly until separateportions of the ring 25 become disposed within each groove 39, so as tobe retained therein by friction, which is preferably increased by sizingthe grooves 39 such that the installed body diameter (i.e., OD_(MAX)) isless than the “free” or un-deflected diameter OD_(F) (FIG. 8).

Although the chuck body 28 is preferably constructed as described above,the chuck 12 may be formed in any other appropriate manner. For example,the chuck body 28 may be provided with two or three narrower clearanceholes or slots 20 separated by arcuate wall sections of substantiallygreater circumferential length, the bit 12 being appropriately formedwith two or three lugs separated by substantial circumferentialclearance. The scope of the present invention encompasses these and allother appropriate structures of the chuck 12 that enable the bitassembly 10 to function at least generally as described herein.

Referring to FIGS. 6, 7 and 12-20, the bit 14 preferably includes a“stepped” body 40 with first and second ends 40 a, 40 b and a centralaxis 42 extending between the two ends 40 a, 40 b. The body first orupper end 40 a is movably coupleable with the chuck 12, specifically bythe interaction of the bit lugs 22 with the retainer 16, such that thebit axis 42 is generally collinear with both the chuck and drill/casingaxis 2 c. The body second or lower end 42 b includes the cutting orworking surface 15. Preferably, the body 40 preferably includes a lower,generally cylindrical portion 42 and an upper, generally tubular portion44 spaced axially from the cylindrical portion 42. The body cylindricalportion 42 has an outer axial end 42 a providing the cutting surface 15and an inner axial end 42 b providing the impact surface 17. Morespecifically, the cylindrical portion outer axial end 42 a has aplurality of generally circular pockets 46 each containing a hardenedcutting insert 48. The body portion inner axial end 42 b has a generallycircular surface 50 providing the impact surface 17 and is strikeable bythe hammer end 3 a, as discussed above and in further detail below.Further, the bit cylindrical portion 42 also preferably has at least oneor more exhaust holes or ports 52 (two depicted), five holes/ports 52being presently preferred (structure not shown), each extending betweenthe first and second axial ends 42 a, 42 b. The exhaust holes 52 providepassages for discharging percussive fluid from the drill casing 2 andare also preferably sized to receive a pusher tool T for displacing thehammer end 3 a from the bit cavity C_(B), as shown in FIG. 22 anddiscussed in greater detail below.

Furthermore, the bit tubular portion 44 has an inner axial end 44 bconnected, preferably integrally formed with, the cylindrical portioninner axial end 42 b, and an opposing outer axial end 44 a, which isengaged/engageable with the chuck body 28. The bit tubular portion 44provides the bit cavity C_(B) and the least one bit lug 22, preferablyfour or more lugs 22 spaced circumferentially about the body axis 42 soas to form a “slotted tube” structure. Specifically, each bit lug 22includes a generally rectangular, cantilever-like body 52 having a firstend 52 a connected, and preferably integrally formed with, an enclosedsidewall portion 54, and a second, free end 52 b spaced axially from thefirst end 52 a. Each lug body 52 has inner and outer, generallycircumferential surfaces 52 c, 52 d, the outer surfaces 52 d of all thebit lugs 36 being located at the bit outside diameter OD_(B), asdiscussed above and in further detail below. Further, each lug free end52 b has a radial end surface 53 contactable with the chuck stop surface35 bounding the clearance hole 34 in which the lug 20 is disposed, so asto thereby prevent axial displacement beyond the bit upper position A₂(as described above), preferably in conjunction with the interactionbetween chuck radial end surfaces 43 and bit slot end surfaces 57.Furthermore, each bit lug body 52 preferably further has two opposingradial contact surfaces 55 each extending axially between the body firstand second ends 52 a, 52 b. Each bit lug contact surface 55 is axiallyslidable against a chuck lug contact surface 41 as the bit 14 movesrelative to the chuck 14, such that the chuck lugs 36 guide thedisplacement of the bit 14 and torque generated by the hammer 3 on thebit 14 is transferred to the chuck 12 at the interface of each contactsurface pair 41/55 (see, e.g., FIG. 6). As the bit assembly 10 has eightcontact surface pairs 41/55 which potentially extend along the entirelength of the mating lugs 22, 36, the contact pressure between the bit14 and the chuck 12 is substantially reduced in comparison withpreviously known bit designs, even though generally only half thesurface pairs 41/55 are used depending on the angular direction ofapplied torque.

Still referring to FIGS. 6, 7 and 12-20, the bit 14 also includes aplurality of elongated, slotted clearance holes 56 each cut or definedbetween adjacent pair of lug bodies 52. Each bit clearance hole 56 has aradial open end 56 a and sized to receive a separate one of the chucklugs 36, as discussed below. Preferably, the lug bodies 52 and clearanceholes 56 extend only partially axially through the body tubular portion44, such that the tubular portion 44 also includes an enclosedcircumferential sidewall section 54, as mentioned above. The enclosedsidewall section 54 is disposed axially between the body cylindricalportion 42 and the plurality of lugs 20, and has an innercircumferential surface 54 a. The wall inner surface 54 a surrounds thehammer end 3 a with clearance when the hammer 3 strikes the bit impactsurface 17, so as to generally constrain or “nest” the hammer end 3 a toprevent lateral movement thereof and to overlap the clearance holes 56to prevent the opening thereof when the bit 14 drops. However, thesidewall section 54 is not required for proper operation of the bitassembly 10 of the present invention.

Referring particularly to FIGS. 11 and 12, each bit lug 22 preferablyincludes an arcuate shoulder 58 disposed generally proximal to the lugbody free end 52 b and engageable or contactable with the retainer 16 toretain the bit 14 movably coupled with the chuck 12. Specifically, eachlug shoulder 58 extends generally circumferentially and axially-inwardlyfrom the bar inner surface 52 c, and includes upper and lower angled ortapered surfaces 60A, 60B and an inner circumferential slide surface 61extending axially between the tapered surfaces 60A, 60B. The lowertapered surface 60B provides the stop surface 23 of each bit lug 20, andis contactable with the retainer catch surface 17 to prevent furtherdownward axial displacement of the bit 14. Further, the shoulder slidesurface 61 is slidable against the retainer central outer surface 29Cwhen the retainer 16 is disposed at the inner radial position R_(I), theshoulder slide surfaces 61 collectively defining a lug shoulder innerdiameter ID_(LS) within which the retainer 16 must be deflected toenable installation and removal of the bit 14.

Further, the lug shoulder tapered surfaces 60A, 60B are also eachconfigured to slide against the lower and upper retainer angled surfaces29B, 29A, respectively, so as to force the retainer body 24 to deflectradially inwardly. Specifically, when the hammer 3 is spaced from theretainer 16, the lug upper surfaces 60A are each disposed against thelower retainer surface 29B, and an upward force F_(U) of a sufficientmagnitude is applied to the bit 14, the lug tapered surfaces 60A allpush against the retainer angled surface 39B to force the retainer body24 to move or deflect toward the inner position R_(I), enabling theshoulder slide surfaces 61 to slide along and past the retainer centralouter circumferential surface 29C, as shown in FIGS. 15-17. Similarly,when the hammer 3 is located externally of the retainer 16, the luglower surface 60B is disposed against the upper retainer surface 29A,and a sufficiently large downward force F_(D) is applied to the bit 14,the lug tapered surface 60B wedges against the retainer angled surface29A so as to push the retainer body 14 generally inwardly toward theinner position R_(I) to permit further downward axial movement of thebit 14.

Although the bit 14 preferably has a body 40 as constructed as describedabove, the bit 14 may alternatively be formed in any other appropriatemanner. For example, the bit 14 may include only two or three “narrow”lugs 22 that engage with appropriately sized chuck clearance slots 20and separated from each other by a substantial clearance space, asdiscussed above with the bit 14. Further for example, the bit lugs 22may be integrally formed directly with the body cylindrical portion 42,such that body tubular portion 44 includes only the lugs 22 (i.e.,without the enclosed sidewall portion 54). Also, the bit lug bodies 52(and clearance openings 56) may extend both axially and radially betweenthe first and second ends 52 a, 52 b so as to be generallyspiral-shaped, and interact with corresponding shaped bit clearanceopenings 20 and lugs 36. With such a structure, the bit 14 will turn orangularly displace as the bit moves axially between the upper and lowerlimit positions, which may be advantageous during a drilling operation.The scope of the present invention encompasses these and all otheralternative structures of the bit 14 that enable the bit assembly 10 tofunction generally as described herein.

Referring to FIGS. 1-5, the skirt 13 preferably includes a generallytubular body 70 having upper end lower radial ends 70 a, 70 b and acentral bore 73 sized to receive the chuck 12 and the bit 14. The skirtbody upper end 70 a is connectable with the casing 2, preferably bysandwiching an inner circumferential shoulder 71 of the skirt betweenthe chuck body upper end 28 a and the casing second end 2 b, and thesecond end 70 b is spaced axially from the casing second end 2 b. Theskirt body 70 has an axial length (not indicated) sufficient to encloseall of chuck clearance openings 20 and the bit clearance holes 56, asbest shown in FIG. 7. As such, the skirt 13 both prevents the prematureexhaust (or reintroduction) of percussive fluid within the drill 1 andprevents debris (e.g., rock cuttings, etc.) from entering into the bitassembly 10.

Referring now to FIGS. 14-22, with the above-described bit assembly 10,the bit 14 is movably coupled with the chuck 12, and alternatelydecoupled or removed from the chuck 12, in generally the followingmanner. To couple or install the bit 14 when separate from the chuck 12,and thus from the drill 1, the hammer lower end 3 a must be displacedaxially upwardly so as to be located externally of, or spaced from, theretainer 16, preferably by means of a pusher tool T as shown in FIG. 22.Then, the bit 14 and chuck 12 are coaxially and angularly aligned suchthat each bit lug free end 52 b is located adjacent to a separate chuckclearance hole open end 34 a and each chuck lug free end 37 b is locatedadjacent to a separate bit clearance hole open end 56 a, as shown inFIG. 14. Thereafter, the bit 14 is axially displaced toward the chuckupper end 28 a (or the chuck 12 toward the bit lower end 40 b) such thatthe bit lugs 22 become increasingly disposed within the chuck openings20 and the chuck lugs 36 move deeper into the bit holes 56, until theshoulder upper surfaces 60A of the bit lugs 22 become disposed againstthe lower tapered surface 29B of the retainer 16, as depicted in FIG.15. At this point, an upward force F_(U) of a sufficient magnitude isapplied to the bit 14 until the retainer 16 is forced to displaceinwardly, as described above, until the bit shoulders 58 displaceaxially upwardly past the retainer 16, as shown in FIGS. 16 and 17.Then, the retainer body 26 is free to deflect radially toward theretainer outer position R_(O), such that the bit lugs 22 are thenconstrained to displace axially within the chuck slotted openings 20,thereby movably coupling or retaining the bit 14 with the chuck 12 bycontact between the retainer catch surface 19 and the bit lug stopsurfaces 23, as shown in FIGS. 18-21.

Referring to FIGS. 2 and 3, in use, the hammer 3 is accelerated byappropriately directed or channeled percussive fluid (e.g., compressedair) to move downwardly toward the bit 14, such that the hammer end 3 aslidably displaces through the chuck 12, enters and moves axially withinthe bit cavity C_(B) until striking the bit impact surface 17. Such ahammer impact pushes the bit 14 to displace generally axially downwardlyrelative to the chuck 12, such that the bit lugs 22 move partiallyoutwardly from the chuck clearance openings 20, forcing the bit cuttingsurface 15 into the work surface S_(W) to fracture material therefrom.The hammer 3 is then displaced axially upwardly by appropriatechanneling of the percussive fluid, and is thereafter repeatedlyreciprocated into striking contact with the bit 14 for the duration of adrilling operation.

When it is desired to remove the bit 14 from the chuck 12, and thus thedrill 1, the hammer lower end 3 a is displaced axially out of theretainer 16 by the pusher tool T, and then bit 14 is axially displaceddownwardly toward the chuck lower end 28 b (or the chuck 12 toward thebit upper end 40 a) such that the bit lugs 22 become increasinglywithdrawn from the chuck openings 20 and the chuck lugs 36 moveoutwardly from the bit holes 56. When the shoulder lower surfaces 60B ofthe bit lugs 22 become disposed against the upper tapered surface 29A ofthe retainer 16, a downward force F_(D) (FIG. 16) of a sufficientmagnitude is applied to the bit 14 to force the retainer 16 to displaceradially inwardly, as described above, until the bit shoulders 58 moveaxially downwardly past the retainer 16. At this point, the bit 14 isdecoupled from the chuck 12, permitting the bit lugs 22 to displacecompletely out of the chuck holes 22, simultaneously withdrawing thechuck lugs 36 out of the bit clearance holes 56, until the bit 14 isseparate from the chuck 12.

The bit assembly 12 of the present invention is clearly advantageous incomparison with previously known bit assemblies. First, the bit 14 isinstalled by relatively simple procedure of pushing the hammer 3 out ofthe assembly, and then applying an axial force sufficient to cause thebit lugs 22 to collapse the preferred snap ring retainer 16. Such aprocedure is much simpler than rotating an entire bit assembly,including the chuck, to threadably disengage the chuck from the casing.In fact, the present bit assembly 10 enables removal of the bit 14without disassembly of the chuck 12. Also, by having a retainer 16 thatmoves or deflects inwardly to release the bit 14, as opposed tooutwardly with the prior art split rings, and which has an inner surfacedisposable against the hammer 3, the chance of an axial load causing aninadvertent release of the bit 14 is substantially reduced. Further, byhaving the chuck 12 and bit 14 engaged by intermeshing axial lugs 22, 36and axial clearance openings 20, 56, as well as a hammer impact surface17 spaced relatively axially close to the cutting surface 15, the bitassembly 10 is much less massive, and requires less material, than priorart bit assemblies. Specifically, previously known bit assemblies had abit with an outer circumferential surface that engaged with a chuckinner circumferential surface, and had a hammer impact surface at aninner end of the bit body, which thus requires a bit of substantiallygreater axial length in comparison with the bit 14 of the presentinvention.

Also, the bit cavity C_(B) provides a “gallery” for exhaustingpercussive fluid such that the fluid is distributed to the bit cuttingsurface 15 in a particular, desired manner. For example, the bit 14 mayinclude a relatively small central hole fluidly coupled with the cavityC_(B) from which two or three (or more) exhaust ports extend to thecutting surface 15 (structure not shown). The bit assembly 10 of thepresent invention may include any number of exhaust ports 52 that evenlydisperse fluid across the bit surface 15 so as to provide improved chipremoval and minimize wear or erosion. Finally, by having a bit 14 thatengages the chuck 12 up to the outer diameter OD_(C), OD_(B) of thebodies 28, 40 of both the chuck 12 and bit 14, torque generated in thebit 14 by hammer impact is transmitted to the chuck 12 at a relativelygreater diameter in comparison with previously known bit designs. Assuch, contact pressures for a given torque are minimized in the presentbit assembly 10, so as to reduce the likelihood of developing fatiguecrack initiation sites from frictional burning.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined in the appended claims.

1. A bit assembly for a drill, the drill including a casing and a hammermovably disposed within the casing and having an end, the bit assemblycomprising: a bit having a cavity; and a retainer connected with thecasing, disposable within the bit cavity, and releasably engageable withbit so as to couple the bit with the casing.
 2. The bit assembly asrecited in claim 1 wherein the retainer includes a generally annularbody having a central opening configured to receive the hammer end suchthat the hammer prevents disengagement of the retainer from the bit whenthe hammer end is disposed within the retainer opening.
 3. The bitassembly as recited in claim 2 wherein the retainer is configured to beat least partially radially displaceable between an outer radialposition at which at least a portion of the retainer is engaged with thebit so as to connect the bit with the casing, and an inner radialposition at which the retainer is generally disengaged from the bit suchthat the bit is disconnectable from the casing, the hammer preventingdisplacement of the retainer to the inner position when the hammer endis disposed within the retainer opening.
 4. The bit assembly as recitedin claim 3 wherein the bit includes a body with a cylindrical portionwith opposing first and second axial ends and a generally tubularportion extending axially from the first end, the tubular portion atleast partially bounding the bit cavity, the cylindrical body first endhaving a cutting surface and the body second end having an impactsurface bounding an axial end of the cavity and strikeable by the hammerend to drive the cutting surface into engagement with a work surface. 5.The bit assembly as recited in claim 4 wherein the bit body cylindricalportion has a hole extending between the first and second axial ends andbeing sized to receive a pusher tool for displacing the hammer end fromthe bit cavity.
 6. The bit assembly as recited in claim 1 furthercomprising a chuck connected with the casing, the retainer being coupledwith one of the chuck and the bit and configured to movably connect thebit with the chuck.
 7. The bit assembly as recited in claim 6 whereinthe chuck has a cavity and the retainer is simultaneously disposablewithin the chuck cavity and the bit cavity.
 8. The bit assembly asrecited in claim 6 wherein: the chuck includes a generally tubular bodywith first and second ends and a central axis extending between the twoends, the first end being connected with the casing and the second endbeing spaced axially from the casing, the body having at least oneopening extending generally axially from the second end toward the firstend; the bit includes a body with a central axis, a cylindrical portion,and a generally tubular portion spaced axially from the cylindricalportion, the tubular portion providing the bit cavity and at least oneaxial lug, the lug being at least partially disposable within the chuckopening; and the retainer is disposable within the bit cavity andengageable with the at least one bit lug so as to releasably couple thebit with the chuck.
 9. The bit assembly as recited in claim 8 wherein:the chuck body includes a plurality of generally axially extending lugsand a plurality of the openings, each opening being defined between aseparate adjacent pair of the chuck axial lugs; and the bit bodyincludes a plurality of the axial lugs and a plurality of generallyaxially-extending openings, each opening being defined between aseparate adjacent pair of the bit axial lugs, each bit axial lug beingdisposable within a separate one of the chuck openings and each bitaxial opening being configured to receive a separate one of the chucklugs such that when bit is coupled with the chuck, the bit lugs moveaxially within the chuck openings and the chuck lugs move axially withinthe bit openings.
 10. The bit assembly as recited in claim 9 wherein:each one of the chuck lugs includes a generally cantilever-like bodyhaving a first end connected with a remainder of the chuck body and asecond, free end spaced axially from the chuck body remainder; and eachone of the bit lugs includes a generally cantilever-like body having afirst end connected with a remainder of the bit body and a second, freeend spaced axially from the bit body remainder.
 11. The bit assembly asrecited in claim 9 wherein each one of the chuck lugs and the bit lugshas two opposing radial contact surfaces and inner and outercircumferential surfaces, the inner surfaces of the bit lugscollectively defining at least a portion of the bit cavity, each bit lugcontact surface being generally slidable against a separate one of thechuck lug contact surfaces.
 12. The bit assembly as recited in claim 9wherein each chuck lug has an inner circumferential surface and agenerally circumferential groove extending outwardly from the innersurface, the retainer being disposed within all of the chuck lug groovesso as connect the retainer with the chuck.
 13. The bit assembly asrecited in claim 9 wherein each bit lug has an inner circumferentialsurface and a generally arcuate shoulder extending generally radiallyinwardly from the inner surface, each shoulder being engageable with theretainer to movably couple the bit with the chuck.
 14. The bit assemblyas recited in claim 13 wherein: the retainer has a radial catch surfacefacing generally toward the chuck upper end; each bit lug shoulder has astop surface facing generally toward the chuck lower end and disposableupon the retainer catch surface so as to prevent axial displacement ofthe bit.
 15. The bit assembly as recited in claim 13 wherein theretainer body is at least partially moveable between inner and outerradial positions; and each lug shoulder has a generally angled releasesurface such that when the hammer end is located externally of theretainer opening and a force of at least a predetermined magnitude isapplied to the bit generally in a direction away from the chuck, theshoulder angled surfaces slide against the retainer body so as displacethe retainer body toward the inner radial position such that the bitdisengages the from the retainer.
 16. A bit assembly for a drill, thedrill having a casing and an axis extending centrally through thecasing, the bit assembly comprising: a chuck including a generallytubular body with first and second ends, the first end being connectedwith the casing such that the second end is spaced axially from thecasing, and at least one opening extending generally axially from thesecond end toward the first end; a bit including a body with a tubularportion, the tubular portion having a cavity and at least one axial lug,the lug being at least partially disposable within the chuck opening;and a retainer coupled with the chuck, disposable within the bit cavityand engageable with the at least one bit lug so as to releasably couplethe bit with the chuck.
 17. The bit assembly as recited in claim 16wherein the chuck has a cavity and the retainer is simultaneouslydisposable within the chuck cavity and the bit cavity.
 18. The bitassembly as recited in claim 16 wherein: the chuck body includes acentral axis, the central axis being coaxial with the casing axis whenthe chuck is connected with the casing, a plurality of generally axiallyextending lugs and a plurality of the openings, each opening beingdefined between a separate adjacent pair of the chuck axial lugs; andthe bit body includes a central axis, the central axis being coaxialwith the bit axis when the bit is coupled with the chuck, a plurality ofthe axial lugs and a plurality of generally axially-extending openings,each opening being defined between a separate adjacent pair of the bitaxial lugs, each bit axial lug being disposable within a separate one ofthe chuck openings and each bit axial opening being configured toreceive a separate one of the chuck lugs such that when bit is coupledwith the chuck, the bit lugs move axially within the chuck openings andthe chuck lugs move axially within the bit openings.
 19. The bitassembly as recited in claim 18 wherein: each one of the chuck lugsincludes a generally cantilever member having a first end connected witha remainder of the chuck body and a second, free end spaced axially fromthe chuck body remainder; and each one of the bit lugs includes agenerally cantilever member having a first end connected with aremainder of the bit body and a second, free end spaced axially from thebit body remainder.
 20. The bit assembly as recited in claim 18 whereineach chuck lug has an inner circumferential surface and a generallycircumferential groove extending outwardly from the inner surface, theretainer being disposed within all of the chuck lug grooves so asconnect the retainer with the chuck.
 21. The bit assembly as recited inclaim 16 wherein the retainer includes a generally annular body having acentral opening configured to receive the hammer end such that hammerprevents disengagement of the retainer from the bit when the hammer endis disposed within the retainer opening.
 22. The bit assembly as recitedin claim 21 wherein the retainer is configured to be at least partiallyradially displaceable between an outer radial position at which at leasta portion of the retainer is engaged with the bit so as to connect thebit with the casing, and an inner radial position at which the retaineris generally disengaged from the bit such that the bit is disconnectablefrom the casing, the hammer preventing displacement of the retainer tothe inner position when the hammer end is disposed within the retaineropening.
 23. A bit assembly for a drill, the drill having a casing, thebit assembly comprising: a chuck including a generally tubular body witha first end connected with the casing, an opposing second end, a centralaxis extending between the two ends, inner and outer circumferentialsurfaces, and at least two through holes each extending generallyaxially from the second end toward the first end and generally radiallybetween the inner and outer surfaces; and a bit including a body with acentral axis, the body having a generally cylindrical portion with acutting surface and at least two cantilever-like lugs extendinggenerally axially from the base portion and spaced circumferentiallyabout the axis, each lug being disposable within a separate one of thechuck through holes, the bit being movably coupled with the chuck suchthat the lugs displace generally axially within the chuck holes as thebit moves axially with respect to the chuck.
 24. The bit assembly asrecited in claim 23 wherein: the chuck body includes a generallycircular sidewall portion, a plurality of generally cantilever-like lugsextending axially from the sidewall portion, and a plurality of theopenings, each opening being defined between a separate adjacent pair ofthe chuck lugs; and the bit body includes a plurality of the bit lugsand a plurality of generally axially-extending openings, each openingbeing defined between a separate adjacent pair of the bit lugs, each bitaxial lug being disposable within a separate one of the chuck openingsand each bit axial opening being configured to receive a separate one ofthe chuck lugs such that when bit is coupled with the chuck, the bitlugs move axially within the chuck openings and the chuck lugs moveaxially within the bit openings.
 25. The bit assembly as recited inclaim 23 further comprising a retainer configured to connect the bitwith the chuck.
 26. The bit assembly as recited in claim 25 wherein: thebit body has a cavity defined generally between the bit lugs; and theretainer is disposable within the bit cavity and releasably engageablewith the bit lugs to removably connect the bit with the chuck.
 27. Thebit assembly as recited in claim 25 wherein: the drill further includesa hammer movably disposed with the casing and having an end contactablewith the bit so as to force the bit cutting surface into engagement witha work surface; and the retainer is at least partially radially inwardlydisplaceable so as to disengage from the bit and further has an openingconfigured to receive a portion of the hammer end such that the hammerprevents radial displacement of the retainer so as to retain the bitcoupled with the chuck.
 28. The bit assembly as recited in claim 23wherein: the drill further includes a hammer movably disposed with thecasing and having an end contactable with the bit so as to force the bitcutting surface into engagement with a work surface; and the bit bodyfurther has a cavity defined generally between the lugs and the bit baseportion has a contact surface partially bounding the bit cavity, thehammer end being disposable within the bit cavity and strikinglycontactable with the bit contact surface.
 29. A bit assembly for adrill, the drill having a casing, the bit assembly comprising: a chuckconnected with the casing and having a generally tubular body, thetubular body having first and second ends, a central axis extendingbetween the two ends, and at least one of an opening extending generallyaxially from the second end toward the first end and a generally axiallug; and a bit having body with a generally tubular portion, the tubularbody portion having a first end connected with a remainder of the bodyand a second end, a cavity extending inwardly from the second end, andat least one of an opening extending generally axially from the secondend generally toward the first end and configured to receive at least aportion of a chuck lug and a generally axial lug disposable within achuck opening; and a retainer coupled with the chuck, disposable withinthe bit cavity and engageable with the bit tubular portion so as toreleasably connect the bit with the chuck.